After decades of worsening diets and sharp increases in obesity, Americans' eating habits have begun changing for the better. Calories consumed daily by the typical American adult, which peaked around 2003, are in the midst of their first sustained decline since federal statistics began to track the subject, more than 40 years ago. The declines cut across most major demographic groups—including higher- and lower-income families, and blacks and whites—though they vary somewhat by group. In the most striking shift, the amount of full-calorie soda drunk by the average American has dropped 25 percent since the late 1990s. As calorie consumption has declined, obesity rates appear to have stopped rising for adults and school-aged children and have come down for the youngest children, suggesting the calorie reductions are making a difference. The reversal appears to stem from people's growing realization that they were harming their health by eating and drinking too much. The awareness began to build in the late 1990s, thanks to a burst of scientific research about the costs of obesity, and to public health campaigns in recent years. The encouraging data does not mean an end to the obesity epidemic: More than a third of American adults are still considered obese, putting them at increased risk of diabetes, heart disease and cancer. Americans are still eating far too few fruits and vegetables and far too much junk food, even if they are eating somewhat less of it, experts say. But the changes in eating habits suggest that what once seemed an inexorable decline in health may finally be changing course. Since the mid-1970s, when American eating habits began to rapidly change, calorie consumption had been on a near-steady incline. Barry Popkin, a University of North Carolina professor who has studied food data extensively, described the development as a "turning point". There is no perfect way to measure American calorie consumption. But three large sources of data about diet all point in the same direction. Detailed daily food diaries tracked by government researchers, data from food bar codes and estimates of food production all show reductions in the calories consumed by the average American since the early 2000s. Those signals, along with the flattening of the national obesity rate, have convinced many public health researchers that the changes are meaningful.

单选题 Which of the following is NOT true according to the first two paragraphs?

单选题 The reversal appeared among Americans because______.

单选题 Which of the disease is NOT related to obesity?

单选题 What can we know from the changes of eating habits?

单选题 What can convince many public health researchers that the changes are meaningful?